A temperature probe frequency response calibration device and method with fast displacement step excitation

Abstract

The application provides a temperature probe frequency response calibration device and method of fast displacement step excitation, the device comprises an experimental section, a calibrated temperature probe, a baffle, a fast displacement mechanism and a photoelectric sensor, the experimental section has stable flow conditions inside, the sensing part of the calibrated temperature probe is arranged in the core area of the experimental section, the movement speed, position and photoelectric sensor signal feedback of the baffle are accurately controlled, the controllability of the heat excitation input time and the accuracy of the heat excitation area are realized. Through the shielding and releasing of the baffle, instantaneous step heat excitation can be generated in millisecond time, the amplitude normalization processing of the output response curve of the calibrated temperature probe is carried out, the dynamic response parameters of the calibrated temperature probe are effectively distinguished, the accuracy of the calibration result is ensured, and the device is suitable for temperature probe frequency response calibration in unsteady flow field measurement.

Description

Technical Field

[0001] This invention belongs to the field of dynamic characteristic calibration technology for temperature probes, specifically relating to a frequency response calibration device and method for a temperature probe with rapid displacement step excitation. It is suitable for dynamic characteristic calibration of temperature probes used in unsteady flow field testing. The designed device and method have controllable thermal excitation input time, clear input amplitude, and accurate thermal excitation region, and can accurately obtain the thermal excitation response of the temperature probe, providing reliable technical support for dynamic temperature measurement in unsteady flow fields. Background Technology

[0002] In unsteady flow field temperature measurement, the temperature changes rapidly over time. Due to the thermal inertia and limited thermal conductivity of the temperature probe's sensing element, the output temperature value differs from the actual temperature value. To select a suitable temperature probe for unsteady flow field experiments, it is necessary to determine the probe's measurement frequency response. However, many parameters affect the temperature probe's measurement frequency response, making accurate theoretical calculations impossible. In practical applications, a temperature probe frequency response calibration device is used to generate a known temperature excitation, study the temperature probe's output characteristics, and thus determine the probe's frequency response.

[0003] Existing dynamic calibration devices for temperature probes, particularly those using wind tunnels as the stable airflow environment generator, typically employ a method of switching between two airflow streams to create varying temperature conditions and apply thermal excitation to the temperature probe. However, the flow field disturbance caused by this switching makes it difficult to precisely control the thermal excitation region experienced by the temperature probe. Furthermore, the uneven temperature gradient and velocity changes during the airflow switching process lead to uncertainty in the thermal excitation input time, affecting the repeatability of the thermal excitation amplitude and intensity, thus making it unstable and impacting the accuracy of the temperature probe's dynamic calibration.

[0004] The laser method heats the sensing part of the temperature probe with laser pulses. Although the laser can accurately define the heating area and clarify the area where the temperature probe receives thermal excitation, for temperature probes with shielding or stagnation designs, the laser cannot directly irradiate the temperature probe sensing element to apply thermal excitation. In addition, since laser thermal excitation is a radiation heat transfer method, it is different from the convective heat transfer mechanism in the actual airflow of turbomachinery. Therefore, it cannot effectively simulate the real working state of the temperature probe in dynamic airflow, thus affecting the reliability of dynamic calibration of the temperature probe.

[0005] Given that the two methods mentioned above each have their advantages and disadvantages, and neither can simultaneously ensure the accuracy of thermal excitation time, region, and amplitude, there is an urgent need for a temperature probe frequency response calibration device and method that integrates controllable thermal excitation input time, precise input region, and identical heat transfer mechanism, so as to achieve temperature probe frequency response calibration and provide reliable technical support for enhancing the understanding of unsteady flow fields. Summary of the Invention

[0006] This invention relates to a frequency response calibration device and method for a temperature probe subjected to rapid displacement step excitation. The device includes an experimental section, a temperature probe to be calibrated, a baffle, a rapid displacement mechanism, and a photoelectric sensor. The experimental section has stable flow conditions, ensuring the repeatability of thermal excitation during the baffle blocking process. The sensing part of the temperature probe to be calibrated is located in the core measurement area of ​​the experimental section. Driven by the rapid displacement mechanism, the baffle moves at high speed in a predetermined direction, blocking or releasing the area directly in front of the sensing part of the temperature probe to be calibrated in a very short time, thus forming a step thermal excitation on the probe. The photoelectric sensor detects the moment when the baffle completely blocks or releases the sensing part of the temperature probe to be calibrated, and uses this moment as the starting time reference for the step thermal excitation. The output curve of the temperature probe to be calibrated is normalized to determine the dynamic response parameters of the temperature probe.

[0007] This invention provides a frequency response calibration device and method for a temperature probe subjected to rapid displacement step excitation. The technical problems to be solved are: First, the uncontrollable thermal excitation input time of existing temperature probe frequency response calibration devices needs to be addressed. Second, the inaccurate thermal excitation effective area of ​​existing temperature probe frequency response calibration devices needs to be addressed. Third, the significant difference between the thermal excitation method of existing temperature probe frequency response calibration devices and the heat transfer mechanism in practical applications needs to be addressed. Fourth, the problem of how differences in thermal excitation amplitude affect the determination of the temperature probe time constant needs to be addressed.

[0008] The technical solution of this invention is:

[0009] 1. A frequency response calibration device for a temperature probe subjected to rapid displacement step excitation, comprising an experimental section (1), a temperature probe to be calibrated (2), a baffle (3), a rapid displacement mechanism (4), and a photoelectric sensor (5), characterized in that the experimental section (1) is a closed pipe for arranging the temperature probe to be calibrated (2) and the baffle (3), the experimental section (1) has stable flow conditions inside, which can ensure the repeatability of thermal excitation during the baffle (3) blocking process, the sensing part of the temperature probe to be calibrated (2) is arranged in the core area of ​​the experimental section (1), the baffle (3) moves at high speed in a straight line along a predetermined direction under the drive of the rapid displacement mechanism (4), and can enter or leave the front of the sensing part of the temperature probe to be calibrated (2) in a very short time, forming an instantaneous blocking or release of the sensing part, and the photoelectric sensor (5) is used to detect the moment when the baffle (3) reaches the predetermined position, and takes the moment as the start time of the step thermal excitation.

[0010] 2. The airflow Mach number of the experimental section (1) is 0.1~2.0, the total airflow temperature is 25℃~1200℃, and the wall is provided with a baffle displacement through hole. The baffle (3) enters or leaves the experimental section (1) through the baffle displacement through hole without damaging the overall sealing of the experimental section (1). The wall of the experimental section (1) is provided with a transparent area. The transparent area is located in the experimental section (1) at a position opposite to the movement path of the baffle (3) to ensure that the photoelectric sensor (5) can receive the light signal reflected from the lower surface of the baffle (3) through the transparent area to accurately determine the displacement position of the baffle (3). The material of the transparent area is optically transparent glass or other optical materials with a light transmittance of not less than 90% to ensure that the photoelectric sensor (5) can stably receive the reflected light signal.

[0011] 3. Displacement velocity of baffle (3) is 2m / s~10m / s, and acceleration is 20m / s². 2 ~80m / s 2 The height is 10 mm to 50 mm, which can cover the sensing part of the temperature probe (2) being calibrated. After the baffle (3) enters the experimental section (1), the rear surface of the baffle (3) and the sensing part of the temperature probe (2) being calibrated maintain a predetermined distance of 2 mm to 6 mm, so that the baffle (3) mainly changes the local heat transfer conditions without mechanically contacting the temperature probe (2) being calibrated. The sudden change in convective heat transfer conditions caused by the baffle (3) blocking or releasing will be equivalent to a negative step or a positive step thermal excitation, respectively.

[0012] 4. An optical reflection area is provided at the lower end of the baffle (3). The shape is rectangular, the width is the same as the width of the baffle (3), and the length is 4 mm to 10 mm. The material is a high reflectivity metal coating or mirror material to ensure that the photoelectric sensor (5) can accurately detect the change in the position of the baffle (3).

[0013] 5. The photoelectric sensor (5) has a signal acquisition frequency of 10kHz~100kHz. The installation position is determined according to the displacement path of the calibrated temperature probe (2), the reference temperature probe (3) and the baffle (3). It ensures that the distance between the edge of the laser beam and the sensing part of the calibrated temperature probe (2) is not less than 1 mm, so as to avoid the laser from generating heat input to the sensing part of the calibrated temperature probe (2). When the baffle (3) starts to block or release the sensing part of the calibrated temperature probe (2), the laser reflection signal is triggered. The start time of the step thermal excitation is determined by detecting the photoelectric trigger signal.

[0014] 6. Based on a rapid displacement step excitation temperature probe frequency response calibration device, the present invention proposes a rapid displacement step excitation temperature probe frequency response calibration method. After completing the installation preparation of each component according to the above requirements, the signal output terminals of the temperature probe (2) to be calibrated and the photoelectric sensor (5) are connected to the signal acquisition system. The signal processing system adopts a unified clock synchronization to ensure that the two sets of signals are in the same time domain. The sampling frequency is not less than 10 times the estimated cutoff frequency of the temperature probe to be calibrated, and not less than the signal acquisition frequency of the photoelectric sensor.

[0015] 7. To ensure that the dynamic response of the applied thermal excitation relative to the calibrated temperature probe (2) is short enough so that the thermal excitation can be regarded as a transient step thermal excitation, the thermal excitation duration must be less than one-tenth of the estimated time constant. Equivalently, the baffle movement speed should satisfy: ,in The velocity of the baffle (3) relative to the sensing part of the temperature probe (2) being calibrated. The characteristic dimension of the sensing part of the temperature probe (2) being calibrated along the direction of movement of the baffle is given. This is the estimated time constant for the temperature probe being calibrated.

[0016] 8. Adjust the Mach number and total temperature of the experimental section (1) to the required operating conditions, set the parameters of the rapid displacement mechanism (4) to adjust the displacement speed, acceleration and direction of the baffle (3), and after the output signal of the temperature probe (2) being calibrated is in a dynamic equilibrium state, turn on the rapid displacement mechanism (4) to make the baffle (3) quickly block or release the sensing part of the temperature probe (2) being calibrated, change the convective heat transfer state at the sensing part of the temperature probe (2) being calibrated, and apply a step thermal excitation input.

[0017] 9. Let the initial time of the step thermal excitation be... The steady-state temperature before the step jump is The steady-state temperature after the step jump is The output of the calibrated temperature probe is .

[0018] 10. Treat the temperature probe to be calibrated as The step response of a step-inertial temperature measurement system is expressed as: ,in: In the formula, For the first A dynamic time constant, This is the weighting coefficient corresponding to the dynamic time constant.

[0019] 11. Therefore: Select on the step response curve Each sampling time: The corresponding temperature probe output is: .

[0020] 12. The first Substitute each sampling point The step response expression is obtained as follows: ,in: Solve this A system of equations is used to obtain the calibrated temperature probe. First-order dynamic response parameters: .

[0021] This invention provides a frequency response calibration device and method for a temperature probe subjected to rapid displacement step excitation, which has the following beneficial effects:

[0022] Beneficial effect 1: The temperature probe frequency response calibration device and method designed in this invention for rapid displacement step excitation can accurately control the input time of thermal excitation by causing heat transfer abrupt change through the blocking and release of the rapid displacement baffle, thus avoiding the calibration error caused by the lag or unstable input time in the existing methods.

[0023] Second beneficial effect: The rapid displacement step excitation temperature probe frequency response calibration device and method designed in this invention ensures that the thermal excitation only acts on the sensing part of the temperature probe through the precise positioning of the baffle. The blocking and releasing of the baffle can precisely control the spatial position of the thermal excitation, thereby improving the stability of the dynamic calibration device.

[0024] Thirdly, the rapid displacement step excitation temperature probe frequency response calibration device and method designed in this invention uses convective heat transfer as the thermal excitation mechanism, which can realistically simulate the actual working state of the temperature probe in dynamic airflow and ensure the reliability of the calibration results.

[0025] Fourthly, the rapid displacement step excitation temperature probe frequency response calibration device and method designed in this invention can obtain accurate thermal excitation input time through photoelectric sensors, and perform amplitude normalization processing on the output response curve of the calibrated temperature probe to eliminate the influence of thermal excitation amplitude fluctuation on the time constant identification result, thus ensuring the accuracy of the calibration result. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of a temperature probe frequency response calibration device for rapid displacement step excitation in an embodiment of the present invention.

[0027] Figure 2 This is a schematic diagram of the installation of an experimental section in an embodiment of the present invention.

[0028] Figure 3 This is a side view of an experimental section installation in an embodiment of the present invention.

[0029] Figure 4 This is a top view of an experimental section installation in an embodiment of the present invention.

[0030] Figure 5 This is the present invention. Figure 4 Sectional view along direction A.

[0031] Among them: 1-experimental section, 2-calibrated temperature probe, 3-baffle, 4-rapid displacement mechanism, 5-photoelectric sensor. Detailed Implementation

[0032] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of the present invention.

[0033] Example 1:

[0034] like Figures 1-5 The figure shows a frequency response calibration device for a temperature probe subjected to rapid displacement step excitation, including an experimental section (1), a temperature probe to be calibrated (2), a baffle (3), a rapid displacement mechanism (4), and a photoelectric sensor (5).

[0035] Experimental section (1) is part of the subsonic wind tunnel system, which provides a stable and adjustable gas and heat environment for experimental section (1). The Mach number of the airflow in experimental section (1) is 0.1, and the total airflow temperature is 200℃. The wall of experimental section (1) is provided with a baffle displacement through hole with a width of 5 mm and a height of 20 mm. The transparent area of ​​the wall of experimental section (1) is 50 mm long and 50 mm wide, located below the movement path of the baffle (3) in experimental section (1), to ensure that the photoelectric sensor (5) can receive the light signal reflected from the lower surface of the baffle (3) through the transparent area. The transparent area is made of optically transparent glass with a light transmittance of 95%.

[0036] The baffle (3) is 20 mm high, 20 mm long, and 5 mm thick. It is made of aluminum alloy and has a smooth surface to ensure accurate blocking effect. The baffle (3) is driven by a rapid displacement mechanism (4). The maximum operating speed of the baffle (3) is 5 m / s and the acceleration is 50 m / s². 2 .

[0037] The temperature probe (2) being calibrated has a diameter of 8 mm and is a K-type bare thermocouple probe.

[0038] The size of the reflective area on the lower surface of the baffle (3) is 10 mm long and 5 mm wide. It is located below the end of the baffle (3) and is rectangular in shape. The material is a high reflectivity metal coating to ensure that the photoelectric sensor (5) can accurately detect the change in the position of the baffle (3). The photoelectric sensor (5) determines the start time of the step thermal excitation by detecting the signal change caused by the reflective area when the baffle (3) completely blocks the calibrated temperature probe (2).

[0039] The baffle (3) quickly blocks the sensing part of the temperature probe being calibrated at a displacement speed of 5 m / s, causing a sudden change in the convective heat transfer conditions, thereby introducing thermal excitation input. The clock synchronously collects the output signals of the temperature probe being calibrated and the photoelectric sensor, and obtains the dynamic response curve of the temperature probe being calibrated.

[0040] Considering a bare K-type thermocouple probe as a first-order thermal inertial system, its step response is expressed as: Two sampling points were selected on the step response curve of the calibrated temperature probe. ,get: , .

[0041] Solving the system of equations, we get: , .

[0042] Example 2:

[0043] In this embodiment, a Pt100 platinum resistance temperature probe is selected as the temperature probe to be calibrated, and the rest of the equipment and parameter settings are the same as in Embodiment 1.

[0044] The Pt100 platinum resistance temperature probe is considered as a second-order thermal inertial system, and its step response is expressed as: Four sampling points were selected on the step response curve of the calibrated temperature probe: .

[0045] We obtain four equations: ,in: Finally, the dynamic response parameters of the calibrated temperature probe are obtained: .

[0046] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A frequency response calibration device for a temperature probe subjected to rapid displacement step excitation, comprising an experimental section (1), a temperature probe to be calibrated (2), a baffle (3), a rapid displacement mechanism (4), and a photoelectric sensor (5), characterized in that, The experimental section (1) is a pipeline for arranging the temperature probe (2) to be calibrated and the baffle (3). The experimental section (1) has stable flow conditions, which can ensure the repeatability of thermal excitation during the baffle (3) blocking process. The sensing part of the temperature probe (2) to be calibrated is arranged in the core area of ​​the experimental section (1). The baffle (3) moves at high speed in a straight line along a predetermined direction under the drive of the rapid displacement mechanism (4). It can enter or leave the front of the sensing part of the temperature probe (2) to be calibrated in a very short time, forming an instantaneous blocking or release on the sensing part. The photoelectric sensor (5) is used to detect the moment when the baffle (3) reaches the predetermined position and take that moment as the start time of the step thermal excitation. The airflow Mach number of the experimental section (1) is 0.1~2.0, and the total airflow temperature is 25℃~1200℃. The wall is provided with a baffle displacement through hole. The baffle (3) enters or leaves the experimental section (1) without damaging the overall sealing of the experimental section (1) through the baffle displacement through hole. The wall of the experimental section (1) is provided with a transparent area. The transparent area is located in the experimental section (1) at a position opposite to the movement path of the baffle (3) to ensure that the photoelectric sensor (5) can receive the light signal reflected from the lower surface of the baffle (3) through the transparent area to accurately determine the displacement position of the baffle (3). The transparent area is made of optically transparent glass or other optical materials with a transmittance of not less than 90% to ensure that the photoelectric sensor (5) can stably receive the reflected light signal. The displacement velocity of the baffle (3) is 2m / s to 10m / s, and the acceleration is 20m / s². 2 ~80m / s 2 The height is 10 mm to 50 mm, which can cover the sensing part of the temperature probe (2) being calibrated. After the baffle (3) enters the experimental section (1), the rear surface of the baffle (3) and the sensing part of the temperature probe (2) being calibrated maintain a predetermined distance of 2 mm to 6 mm, so that the baffle (3) mainly changes the local heat transfer conditions without mechanically contacting the temperature probe (2) being calibrated. The sudden change in convective heat transfer conditions caused by the baffle (3) blocking or releasing will be equivalent to a negative step or a positive step thermal excitation, respectively. An optical reflection area is provided at the lower end of the baffle (3). The area is rectangular in shape, with the same width as the baffle (3) and a length of 4 mm to 10 mm. The material is a high-reflectivity metal coating or a mirror material to ensure that the photoelectric sensor (5) can accurately detect the change in the position of the baffle (3). The photoelectric sensor (5) has a signal acquisition frequency of 10kHz~100kHz. The installation position is determined according to the displacement path of the calibrated temperature probe (2), the reference temperature probe (3) and the baffle (3). It ensures that the distance between the edge of the laser beam and the sensing part of the calibrated temperature probe (2) is not less than 1 mm, so as to avoid the laser from generating heat input to the sensing part of the calibrated temperature probe (2). When the baffle (3) starts to block or release the sensing part of the calibrated temperature probe (2), the laser reflection signal is triggered. The start time of the step thermal excitation is determined by detecting the photoelectric trigger signal.

2. According to the rapid displacement step excitation temperature probe frequency response calibration device as described in claim 1, a rapid displacement step excitation temperature probe frequency response calibration method is proposed. After completing the installation preparation of each component according to the above requirements, the signal output terminals of the temperature probe (2) to be calibrated and the photoelectric sensor (5) are connected to the signal acquisition system. The signal processing system adopts a unified clock synchronization to ensure that the two sets of signals are in the same time domain. Its sampling frequency is not less than 10 times the estimated cutoff frequency of the temperature probe to be calibrated, and not less than the signal acquisition frequency of the photoelectric sensor. To ensure that the dynamic response of the applied thermal excitation relative to the calibrated temperature probe (2) is sufficiently short, thus allowing the thermal excitation to be considered as a transient step thermal excitation, the thermal excitation duration must be less than one-tenth of the estimated time constant. Equivalently, the baffle movement speed should satisfy: ,in The velocity of the baffle (3) relative to the sensing part of the temperature probe (2) being calibrated. The characteristic dimension of the sensing part of the temperature probe (2) being calibrated along the direction of movement of the baffle is given. The estimated time constant of the temperature probe being calibrated; Adjust the Mach number and total temperature of the experimental section (1) to the required operating conditions, set the parameters of the rapid displacement mechanism (4) to adjust the displacement speed, acceleration and direction of the baffle (3), and after the output signal of the calibrated temperature probe (2) is in a dynamic equilibrium state, turn on the rapid displacement mechanism (4) to make the baffle (3) quickly block or release the sensing part of the calibrated temperature probe (2), change the convective heat transfer state at the sensing part of the calibrated temperature probe (2), and apply a step thermal excitation input. Let the start time of the step thermal excitation be The steady-state temperature before the step jump is The steady-state temperature after the step jump is The output of the calibrated temperature probe is ; The temperature probe to be calibrated is regarded as The step response of a step-inertial temperature measurement system is expressed as: ,in: In the formula, For the first A dynamic time constant, The weighting coefficients corresponding to this dynamic time constant; therefore: Select on the step response curve Each sampling time: The corresponding temperature probe output is: ; The first Substitute each sampling point The step response expression is obtained as follows: ,in: Solve this A system of equations is used to obtain the calibrated temperature probe. First-order dynamic response parameters: .

Images